ASP.Net Web API uses all the features of HTTP like URIs, request/response headers, various content formats caching, versioning and there is no need to define any extra configuration settings for different devices like WCF rest services.

ASP.Net Web API communicate with HTTP/HTTPs

The basic CRUD operations are mapped to the HTTP protocols in the following manner:
GET: This will be used to retrieve the required data from the remote resource.
POST: This will create a new entry for the current data that is being sent to the server.
PUT: This will update the current representation of the data on the remote server.
DELETE: This will delete the specified data from the remote server.

Features of ASP.NET WEB API
-It can be hosted with in the applicaion or on IIS.
-It has automatic support for OData.
-It supports convention-based CRUD Actions